Late on Friday, a federal district judge in Texas, Reed O'Connor, dropped a bomb on the Affordable Care Act, and indeed on the entire American health care system.

His ruling, in Texas v. U.S., was a victory for the 20 Republican state attorneys general and governors who had brought the case in February, asking the court to block operation of the health care law. They based their attack on the law's requirement that people either buy health insurance or pay a penalty, which opponents of the law have long called an unconstitutional mandate.

In a landmark decision in 2012, the Supreme Court upheld the law by declaring that mandate was actually a tax, which Congress had the authority to impose. But when Congress reduced the tax to zero last year, the plaintiffs argued that now -- without its individual-responsibility enforcement mechanism -- the entire Affordable Care Act was suddenly unconstitutional.

Judge O'Connor agreed. He said further that the law and its mandate could not be separated, and with this key part missing, the whole law should collapse, like a pillar of blocks in the game Jenga.

The scope of Judge O'Connor's judgment is breathtaking. The ACA contains ten titles and hundreds of individual provisions governing every corner of our health care system. The invalidation of the ACA, if upheld on appeal, would affect virtually every American.

Of course, millions of individuals who purchase their insurance directly from insurers or through the marketplaces would lose the ACA's preexisting condition protections. Older Americans and women could again be discriminated against as well.

Millions of individuals and families covered through the ACA's Medicaid expansions would lose coverage — even in states that have recently passed referenda to expand coverage — but other Medicaid beneficiaries would lose benefits conferred by the ACA as well.

Medicare beneficiaries would lose preventive-services coverage and could see the "donut hole" reopen, imposing higher drug costs. Indeed, the order may invalidate current ACA regulations governing Medicare payments, throwing the Medicare program into chaos.

Most Americans, who have coverage through their employer, would lose their right to preventive services and coverage of children to age 26 and see lifetime and annual dollar limits of coverage reappear. ACA reforms to the Indian Health Service or provisions for FDA approval of generic biologic drugs would disappear. Fraud and abuse protections included in the ACA would no longer be effective.

In deciding to wreak this destruction on the American health care system, Judge O'Connor arrogated to himself authority that rightly belongs with Congress. A Republican Congress spent most of 2017 debating to what extent it wanted to repeal the ACA. In the end, it only changed one small provision: reducing the shared responsibility tax to $0.

Judge O'Connor believes that in doing so, Congress pulled a grenade pin, exploding the entire law. But numerous Republicans, both during the debate on the vote on the tax law and since, have made it clear that was not what they did.

Judge O'Connor points to the "findings" from the original ACA itself to claim that the mandate was "essential" to various provisions of the law, but those findings were included to bolster arguments that the mandate was constitutional as a legal requirement and were not intended to make the rest of the law dependent on the mandate.

Republicans in Congress repeatedly tried and failed to repeal the ACA. It is not up to an unelected judge to do it himself.

So, what does Judge O'Connor's judgment mean? He specifically did not enter an order blocking the operation of the law, so it remains in effect. O'Connor only found two individuals had standing to challenge the law, so arguably the ruling only applies to them.

Another judge is considering a case brought by Maryland to uphold the ACA, so we may get dueling judgments. An earlier appellate court decision, involving a number of the states in this case, invalidated the individual mandate but held the entire remainder of the ACA to be valid. Any noncompliance with the law may be challenged in other courts.

California will appeal Judge O'Connor's decision and the Trump administration may appeal parts of it as well. It will likely be reversed on appeal and may never get to the Supreme Court. It is simply the opinion of one district court judge.

But it will surely cause chaos and confusion throughout the health care system, as the federal government's lawyer predicted at oral arguments. No doubt that is what Judge O'Connor wanted.